Applicant claims, under 35 U.S.C. xc2xa7119, the benefit of priority of the filing date of Apr. 25, 1998 of a European patent application, copy attached, Ser. No. 98107582.3, filed on the aforementioned date, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a measuring device for measuring the accuracy of the position and track of a machine element moved along a predetermined linear track, having a length measuring device for measuring the position of the machine element along the linear track.
2. Discussion of Related Art
The measuring of industrial robots is gaining increasing importance in connection with the continuing shifts in computer-integrated production. The demands on the accuracy of position and tracks made in actual use are, as a rule, not met without prior measuring and calibration of each individual robot specimen. At present, a robot-like structure with several rotary axes is also increasingly employed as a measuring machine. Such a measuring machine can be used in the same way as a normal coordinate-measuring machine for the measuring of workpieces. But it can be used particularly advantageously for measuring and calibrating industrial robots, such as has been described in EP 0 615 110 B1 and EP 0 533 949 A1, for example.
As a rule, such robot-like measuring machines must also be measured and calibrated prior to being used.
A measuring device for measuring the position and track accuracy of a robot on which the invention is based is described in DE 37 10 068 C2. The positioning accuracy of a tool receptacle (end effector) of the robot is measured in a contactless manner by means of a laser alignment measuring device. A laser interferometer, an optical measuring head with position-sensitive detectors and an evaluation unit are parts of this measuring device. The optical measuring head is fastened on the tool receptacle of the robot or of a machine tool. The straightness of the laser beam exiting the interferometer is used as a reference. The measuring head is moved along this laser beam for the measurement. In the process, the measuring device registers kinematic characteristic values as well as geometric characteristic values. Deviations from the predetermined track along the laser beam are measured by means of the interferometer and are measured transversely in respect to it by means of the position-sensitive detectors. A computer takes over the measured values and calculates robot-specific characteristic values from them.
The disadvantage of this measuring device is that for many applications these characteristic values cannot be measured with sufficient precision. Moreover, this measuring device requires a drive of the machine element to be tested. Thus, an automatic measurement of measuring machines that do not have an individual drive is not possible.
One aspect of the present invention regards a measuring system for measuring the accuracy of the position and track of a machine element moved along a predetermined track. The system includes a predetermined track along which a machine element moves relative thereto and a measuring device for measuring the position of the machine element along the track. The track has a guide of the measuring device, on which a carriage is guided along the track, wherein the machine element can be fastened to the carriage. A component of the measuring device is fastened on the carriage and a drive integrated with the measuring device moves the carriage in a controlled manner along the guide into predetermined positions and at predetermined speeds.
A second aspect of the present invention regards a measuring system for measuring the accuracy of the position and track of a machine element, which is seated, displaceable and/or rotatable in several axes in space. The measuring system includes a guide that predetermines a track in space and along which a carriage is guided along the track. A component of a measuring device is fastened on the carriage for measuring the position of the carriage along the track and a drive is integrated with the measuring device that displaces the carriage in a controlled manner along the guide into predetermined positions and at predetermined speeds. The carriage is rigidly coupled with the machine element in a plurality of axial directions to be tested, in which the machine element is seated, displaceable and/or rotatable in space.
One advantage and object of each aspect of the present invention is to provide a measuring system for measuring the accuracy of the position and track of a moved machine element, which can be flexibly employed, has a high degree of measuring accuracy, and with which it is also possible in a simple manner to test and calibrate measuring machines which do not have an individual drive.
Another advantage and object of each aspect of the present invention is to allow for the measurement and calibration of industrial robots, as well as of manually guided and in particular robot-like measuring machines, wherein the automation of the measuring and calibrating method is made possible. With constant orientation, the position and track accuracy, and in particular the accurate reproducibility, can be registered in a highly accurate manner, since the moving machine element to be tested is rigidly moved along the measuring track by the measuring device itself. In this case a change in the orientation cannot occur at all, or respectively only to a negligible extent.
Further objects, advantages and details of the measuring system according to the invention will become apparent from the ensuing description of an exemplary embodiment in conjunction with the accompanying drawings.